This invention relates to an image forming apparatus such as a digital copying machine which includes a fixing device having contained therein a heat generating member heated by an induction heating device using a coil, for example.
Conventionally, in an image forming apparatus such as a digital copying machine, a fixing device which fixes a developer image on paper is used. The fixing device of the digital copying machine includes a heating roller and a pressure roller which is placed in contact with the heating roller. The fixing device fixes a developer image on a sheet of paper by use of heat of the heating roller while inserting the sheet of paper in between the heating roller and the pressure roller and feeding the same.
As one example of the heat source of the heating roller, an induction heating device is provided. In the fixing device used in the conventional digital copying machine, an induction heating device which heats the whole portion of the heating roller is used. However, in the above fixing device, it is necessary to heat the whole portion of the heating roller even when an image is present only on part of the sheet of paper, that is, when a developer exists only on part of the sheet of paper. Therefore, electric power tends to be wasted.
This invention is made to solve a problem that electric power tends to be wasted when an image is present only on part of the sheet of paper as described above, and an object of this invention is to provide a fixing device and an image forming apparatus in which a fixing process can be efficiently performed without wasting electric power.
A fixing device of this invention which fixes a to-be-fixed agent on an image-forming medium comprises a heat roller which has a plurality of heaters contained therein and corresponding portions of which are heated by selectively supplying electric power to the heaters, an image area determining section which determines whether a fixing process is necessary or not for each of areas corresponding to the portions of the heat roller respectively heated by the heaters based on an image to be fixed on the image-forming medium, and a fixing control section which supplies preset electric power only to the heater corresponding to the area which is determined to require the fixing process by the image area determining section to set the corresponding portion on the heat roller to a fixing temperature and fixes the to-be-fixed agent on the image-forming medium when the portion on the heat roller corresponding to the heater supplied with the preset electric power has reached a preset fixing temperature.
An image forming apparatus of this invention which forms an image on an image-forming medium by use of a developer comprises an image input section which inputs image data, an optical unit which applies light to an image carrier to expose the image carrier to light according to image data input by the image input section, a transferring section which transfers a developer image corresponding to an electrostatic latent image formed on the image carrier by applying light thereto by the optical unit onto the image-forming medium, a fixing device including a heat roller which has a plurality of heaters contained therein and corresponding portions of which are heated by selectively supplying electric power to the heaters, an image area determining section which determines whether a fixing process is necessary or not for each of areas corresponding to the portions of the heat roller respectively heated by the heaters based on image data input by the image input section, a heater control section which supplies preset electric power only to the heater corresponding to the area which is determined to require the fixing process by the image area determining section to set the corresponding portion on the heat roller to a fixing temperature, and a printing control section which feeds the image-forming medium having the developer image transferred thereon by the transferring section to the fixing device and fixes the to-be-fixed agent on the image-forming medium by use of the heat roller when the portion on the heat roller corresponding to the heater supplied with the electric power by the heater control section has reached a preset fixing temperature.
A fixing device of this invention which fixes a to-be-fixed agent on an image-forming medium comprises heating means which has a plurality of heaters contained therein and corresponding portions of which are heated by selectively supplying electric power to the heaters, image area determining means for determining whether a fixing process is necessary or not for each of the areas corresponding to the portions on the heating means respectively heated by the heaters based on an image to be fixed on the image-forming medium, and fixing control means for supplying preset electric power only to the heater corresponding to the area which is determined to require the fixing process by the image area determining means to set the corresponding portion on the heating means to a fixing temperature and fixes the to-be-fixed agent on the image-forming medium when the portion on the heating means corresponding to the heater supplied with the preset electric power has reached a preset fixing temperature.
An image forming apparatus of this invention which forms an image on an image-forming medium by use of a developer comprises image input means for inputting image data, optical control means for applying light to an image carrier to expose the image carrier to light according to image data input by the image input means, transferring means for transferring a developer image corresponding to an electrostatic latent image formed on the image carrier by applying light thereto by the optical control means onto the image-forming medium, fixing means including a heat roller which has a plurality of heaters contained therein and corresponding portions of which are heated by selectively supplying electric power to the heaters, image area determining means for determining whether a fixing process is necessary or not for each of the areas corresponding to the portions on the heat roller respectively heated by the heaters based on image data input by the image input means, heater control means for supplying preset electric power only to the heater corresponding to the area which is determined to require the fixing process by the image area determining means to set the corresponding portion on the heat roller to a fixing temperature, and printing control means for feeding the image-forming medium having the developer image transferred thereon by the transferring means to the fixing means and fixing the to-be-fixed agent on the image-forming medium by use of the heat roller when the portion on the heat roller corresponding to the heater supplied with the electric power by the heater control means has reached a preset fixing temperature.
A fixing method of this invention used in a fixing device including a heat roller which has a plurality of heaters contained therein and corresponding portions of which are heated by selectively supplying electric power to the heaters comprises determining whether a fixing process is necessary or not for each of areas corresponding to the portions on the heat roller respectively heated by the heaters based on an image to be fixed on an image-forming medium, supplying preset electric power only to the heater corresponding to the area which is determined to require the fixing process by the determining step to set the corresponding portion on the heating means to a fixing temperature, and fixing the to-be-fixed agent on the image-forming medium when the portion on the heat roller corresponding to the heater supplied with the preset electric power has reached a preset fixing temperature.
An image forming method of this invention used in an image forming apparatus using a fixing device including a heat roller which has a plurality of heaters contained therein and corresponding portions of which are heated by selectively supplying electric power to the heaters comprises inputting image data, applying laser light to an image carrier to expose the image carrier to light according to the input image data, transferring a developer image corresponding to an electrostatic latent image formed on the image carrier onto the image-forming medium, determining whether a fixing process is necessary or not for each of the areas corresponding to the portions on the heat roller respectively heated by the heaters based on the input image data, supplying preset electric power only to the heater corresponding to the area which is determined to require the fixing process by the determining step to set the corresponding portion on the heat roller to a fixing temperature, and feeding the image-forming medium having the developer image transferred thereon and fixing the to-be-fixed agent on the image-forming medium when the portion on the heat roller corresponding to the heater supplied with the electric power has reached a preset fixing temperature.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.